TWI748147B - Method for making graphene adhesive film and method for transferring graphene - Google Patents

Abstract

A method for making a graphene adhesive film including the steps of: growing a graphene on a growth substrate made of copper; coating an adhesive layer on the surface of the graphene away from the growth substrate; and removing the growth substrate by using an etching solution which is a mixture of hydrogen peroxide, hydrochloric acid, and deionized water. The present application also relates to a method for transferring the graphene.

Description

Preparation method of graphene glue film and transfer method of graphene

The invention relates to a method for preparing a graphene glue film and a method for transferring graphene.

In the prior art, graphene can be prepared by methods such as mechanical exfoliation, silicon carbide epitaxial growth, oxidation-reduction, and chemical vapor deposition. Among them, the chemical vapor deposition method using copper metal as the growth substrate is easy to synthesize graphene with large area, uniformity, high quality and controllable layer number, so this method is widely used.

At present, the most commonly used method to transfer graphene from a copper growth substrate to a target substrate is to use polymethylmethacrylate (PMMA) or heat release tape as a support material, and use ferric chloride solution or ferric nitrate solution to corrode After the copper substrate is grown, the graphene and the supporting material are transferred to the target substrate, and the supporting material is finally removed. However, in actual operation, when ferric chloride solution or ferric nitrate solution corrodes copper, iron ions will be oxidized into iron oxide particles, and copper will also be oxidized into copper oxide particles. The iron oxide particles and copper oxide particles are not acceptable. Avoid ground will remain on the surface of the graphene and cause pollution to the graphene, thereby affecting the performance of the graphene.

In the article "Toward Clean and Crackless Transfer of Graphene", Liang et al. disclosed a method for cleaning the PMMA/graphene composite layer after etching the copper growth substrate with ferric nitrate solution to obtain the PMMA/graphene composite layer. The method of cleaning the PMMA/graphene composite layer is: the first step is to rinse with deionized water; the second step is to etch with SC-2 solution for 15 minutes; the third step is to rinse with deionized water; the fourth step is to use The SC-1 solution is corroded for 15 minutes; the fifth step is to rinse with deionized water. The SC-2 solution is a mixed solution of deionized water, hydrogen peroxide and hydrochloric acid, and H ₂ O: H ₂ O ₂ : HCl (volume ratio)=20:1:1. The SC-1 solution is a mixed solution of deionized water, hydrogen peroxide and ammonia, and H ₂ O: H ₂ O ₂ : NH ₄ OH (volume ratio)=20:1:1. However, Liang et al. still use a conventional solution (ferric nitrate solution) to corrode the copper growth substrate, and the step of corroding the copper growth substrate will still cause pollution to graphene.

In view of this, it is necessary to provide a method for preparing a graphene film and a method for transferring graphene. The method makes it necessary that the graphene transferred to the target substrate does not have residual iron oxide and copper oxide particles.

A method for preparing a graphene adhesive film, comprising the following steps: growing a graphene on a growth substrate, the material of the growth substrate is copper; coating an adhesive layer on the surface of the graphene away from the growth substrate, Forming an adhesive/graphene/growth substrate composite structure; and using an etching solution to remove the growth substrate of the adhesive/graphene/growth substrate composite structure, the etching solution being hydrogen peroxide, hydrochloric acid and deionized water的mixture.

A method for transferring graphene, comprising the following steps: growing a graphene on a growth substrate; coating an adhesive layer on the surface of the graphene away from the growth substrate to form a growth substrate/graphene/ Adhesive composite structure; using an etching solution to remove the growth substrate to form a graphene/adhesive composite layer, the etching solution is a mixture of hydrogen peroxide, hydrochloric acid and deionized water; the graphene/ The adhesive composite layer is arranged on a target substrate, and the graphene is in direct contact with the target substrate; and the adhesive layer is removed.

Compared with the prior art, in the preparation method of graphene film and graphene transfer method provided by the present invention, a mixture of hydrogen peroxide, hydrochloric acid and deionized water is used as an etching solution to corrode the copper growth substrate, thereby making the transfer to The graphene on the target substrate is pure, with no iron oxide, copper oxide and other particles remaining.

100: growth base

200: Graphene

300: Adhesive layer

400: Graphene film

500: container

600: Corrosive liquid

700: target base

FIG. 1 is a process flow diagram of a method for preparing a graphene film provided by the first embodiment of the present invention.

Fig. 2 is an optical photograph of the etching solution provided by the first embodiment of the present invention.

Fig. 3 is another optical photograph of the etching solution provided by the first embodiment of the present invention.

4 is an optical photograph of the graphene/adhesive composite structure provided by the first embodiment of the present invention.

FIG. 5 is a process flow diagram of a method for removing a growth substrate using an etching solution according to the first embodiment of the present invention.

Fig. 6 is a process flow diagram of a graphene transfer method provided by a second embodiment of the present invention.

FIG. 7 is an optical photograph of graphene after transfer using a ferric chloride solution as an etching solution provided by the second embodiment of the present invention.

FIG. 8 is a scanning electron micrograph of graphene after transfer using ferric chloride solution as the etching solution provided by the second embodiment of the present invention.

FIG. 9 is an optical photograph of graphene after transfer using a mixture of hydrogen peroxide, hydrochloric acid and deionized water as the etching solution provided by the second embodiment of the present invention.

FIG. 10 is a scanning electron microscope photograph of graphene after transfer using a mixture of hydrogen peroxide, hydrochloric acid and deionized water as the etching solution provided by the second embodiment of the present invention.

FIG. 11 is a Raman spectrum diagram of graphene after transfer using a mixture of hydrogen peroxide, hydrochloric acid and deionized water as the etching solution provided by the second embodiment of the present invention.

The method for preparing the graphene film and the method for transferring graphene provided by the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

1 to 5, the present invention provides a method for preparing a graphene film 400, which includes the following steps: S11, growing a graphene 200 on a growth substrate 100; S12, where the graphene 200 is far away from the growth substrate The surface of 100 is coated with an adhesive layer 300; and S13, an etching solution 600 is used to remove the growth substrate 100.

In step S11, the material of the growth substrate 100 is copper, and the size of the growth substrate 100 is not limited and can be selected according to actual conditions. In this embodiment, the growth substrate 100 is a copper sheet. Preferably, the hydrophilic treatment of the growth substrate 100 can make the graphene 200 grown more smooth without wrinkles. The method of hydrophilic treatment includes the following steps: firstly, the growth substrate 100 is cleaned, When washing, use the standard process of ultra-clean room to clean. Then, the growth substrate 100 is treated with microwave plasma. Specifically, the growth substrate 100 can be placed in a microwave plasma system, and an induction power source of the microwave plasma system can generate oxygen plasma, chlorine plasma or argon plasma. The plasma diffuses from the generation area and drifts to the surface of the growth substrate 100 with lower ion energy, thereby improving the hydrophilicity of the growth substrate 100.

The method of growing the graphene 200 on the growth substrate 100 is not limited. In this embodiment, the process of growing graphene 200 on the growth substrate 100 is as follows: depositing a catalyst layer on the growth substrate 100, and then placing the growth substrate 100 on which the catalyst layer is deposited into a reaction chamber, and introducing carbon source gas, The reaction chamber is heated to 800° C. to 1000° C., so that graphene 200 is grown on the growth substrate 100.

A layer of metal or metal compound material is deposited on the surface of the growth substrate 100 to form the catalyst layer. The metal can be one or any combination of gold, silver, copper, iron, cobalt, and nickel. The metal compound may be one or any combination of zinc sulfide, zinc oxide, ferric nitrate, ferric chloride, and copper chloride. The method of depositing the catalyst layer on the growth substrate 100 is not limited, such as chemical vapor deposition, physical vapor deposition, vacuum thermal evaporation, magnetron sputtering, plasma enhanced chemical vapor deposition or printing.

The reaction chamber is a closed cavity, and the closed cavity has an air inlet and an air outlet. The gas inlet is used for introducing reaction gas, such as carbon source gas, etc., and the gas outlet is communicated with a vacuum pumping device. The vacuum device controls the vacuum degree and air pressure of the reaction chamber through the air outlet. Further, the reaction chamber may also include a water cooling device and a heating device for controlling the temperature in the reaction chamber. In this embodiment, the reaction chamber is a quartz tube.

The carbon source gas may be a compound such as methane, ethane, ethylene or acetylene. Non-oxidizing gases such as hydrogen can be introduced into the reaction chamber. With the continuous introduction of non-oxidizing gas, when the temperature in the reaction chamber is 800° C. to 1000° C., the carbon source gas is cracked, and carbon atoms are deposited on the surface of the catalyst layer to form graphene 200. The gas flow rate of the carbon source gas is 20 sccm (standard condition milliliters per minute) to 90 sccm, and the gas flow ratio of the non-oxidizing gas to the carbon source gas ranges from 45:2 to 15:2. The reaction chamber can also be in a vacuum environment, and the pressure is 10 ^-1 to 10 ² Pa. The constant temperature time for growing graphene 200 ranges from 10 minutes to 60 minutes. In this embodiment, the air pressure in the reaction chamber is 500 mTorr, the reaction temperature is 1000 degrees Celsius, the carbon source gas is methane, the gas flow rate is 25 sccm, and the constant temperature time is 30 min.

In step S12, the material of the adhesive layer 300 is not limited, such as polymethylmethacrylate (PMMA), heat release tape, or polyvinyl acetal. The polyvinyl acetal includes polyvinyl formal PVF or polyvinyl butyral PVB. The method of setting the adhesive layer 300 is not limited, such as spin coating or deposition. The thickness of the adhesive layer 300 is not limited. 150 nanometers to 2 micrometers thick The PMMA is spin-coated on the surface of the graphene 200 away from the growth substrate 100, and baked at a temperature of 60°C to 200°C for 1 minute to 10 minutes or placed at room temperature for 30 minutes to 60 minutes to obtain an adhesive/graphite Ane/growth substrate composite structure. In this embodiment, 200 nm thick PMMA is spin-coated on the surface of the graphene 200 away from the growth substrate 100, and baked at a temperature of 180° C. for 2 minutes to obtain the adhesive/graphene/growth substrate composite structure. The adhesive/graphene/growth substrate composite structure includes an adhesive layer 300, graphene 200, and a growth substrate 100, and the graphene 200 is located between the growth substrate 100 and the adhesive layer 300. That is, the graphene 200 has two opposite surfaces, one surface is in direct contact with the growth substrate 100, and the other surface is in direct contact with the adhesive layer 300.

In step S13, the etching solution 600 is _{a mixed solution of hydrogen peroxide (hydrogen peroxide H 2} O ₂ ), hydrochloric acid (HCL), and deionized water (DIW). Among them, the role of hydrogen peroxide is mainly to oxidize copper, and the role of hydrochloric acid is to maintain an acidic environment. The volume ratio of hydrogen peroxide, hydrochloric acid and deionized water is: H ₂ O ₂ :HCL:DIW=1:1-5:30-100. In this embodiment, the volume ratio of hydrogen peroxide, hydrochloric acid and deionized water is: H ₂ O ₂ :HCL:DIW=1:1:50. There will be a small amount of bubbles in the mixed solution of H ₂ O ₂ , HCL and DIW. As shown in FIG. 2, the bubbles will affect the corrosion rate of the copper growth substrate 100. Diluting the etching solution 600 can reduce bubbles. When the volume ratio of hydrogen peroxide, hydrochloric acid and deionized water is: H ₂ O ₂ :HCL:DIW=1:1:50, the etching solution 600 has almost no bubbles. In addition, in order to increase the corrosion rate of the copper growth substrate 100, in this embodiment, a dropper is used to drive away the bubbles in the mixed solution, that is, there are no bubbles in the mixed solution in this embodiment, as shown in FIG. 3 Show. When preparing the etching solution 600, _{the mixing sequence of H 2} O ₂ , HCL and DIW is not limited.

In addition, the volume ratio of hydrogen peroxide and hydrochloric acid is preferably 1:1. Of course, the volume ratio of hydrogen peroxide and deionized water cannot be greater than or equal to 1:20, and the volume ratio of hydrochloric acid and deionized water cannot be greater than or equal to 1:20. When the volume ratio of hydrogen peroxide and deionized water is greater than or equal to 1:20, and the volume ratio of hydrochloric acid and deionized water is greater than or equal to 1:20, when the etching solution 600 is corroding the copper growth substrate 100, the etching solution and the copper The reaction is violent, and a large number of bubbles will be generated. These bubbles will destroy the structural integrity of the graphene 200 and cause the graphene 200 to rupture. The graphene/adhesive composite structure shown in FIG. 4 is _{a growth substrate 100 etched with a mixture of H 2} O ₂ :HCL:DIW (volume ratio)=1:1:20. It can be seen from FIG. 4 that the graphene/adhesive composite structure (the composite structure of the graphene 200 and the adhesive layer 300) is broken and does not constitute a complete film-like structure.

Referring to FIG. 5, the method of using the etching solution 600 to remove the growth substrate 100 includes the following steps: S131, containing the etching solution 600 in an open container 500; S132, putting the adhesive/graphene/growth substrate composite structure in step S12 into the etching solution 600, and the adhesive layer 300 is located in the graphite Above the olefin 200, the growth substrate 100 is located below the graphene 200; S133, maintaining a period of time so that the growth substrate 100 is completely corroded to form a graphene film 400, which floats on the etching solution 600 Surface; and S134, removing the graphene film 400 from the etching solution 600.

In step S132, preferably, the entire adhesive/graphene/growth substrate composite structure is suspended in the etching solution 600 and soaked.

In step S133, the graphene film 400 is a composite structure of graphene 200 and adhesive layer 300.

After taking the graphene film 400 out of the etching solution 600, it further includes: repeatedly soaking and washing with deionized water for several times, and then air-drying the graphene film 400 naturally to obtain a graphene film 400 that is easy to store.

The graphene adhesive film 400 includes graphene 200 and an adhesive layer 300, the graphene 200 and the adhesive layer 300 are stacked, and the graphene 200 and the adhesive layer 300 are in direct contact. In the graphene film 400, the adhesive layer 300 functions mainly to provide support and protection for the graphene 200. The graphene film 400 is a flexible self-supporting film.

The preparation method of the graphene film 400 has the following advantages: First, a mixture of hydrogen peroxide, hydrochloric acid, and deionized water is used as the etching solution 600 to corrode the copper growth substrate 100, so that the graphene 200 is pure and free of iron oxide. , Copper oxide and other particles exist; secondly, in the graphene film 400, the adhesive layer 300 has good viscosity and support, and has stable chemical properties, so that the graphene film 400 is self-supporting , Can be directly stored in a clean storage box, which is conducive to storage and subsequent use; third, the graphene film 400 is self-supporting, not only can be cut, but also can be directly used to clamp the graphene film 400 with tweezers and other clamps. Attach it to any desired target substrate, and then use an organic solvent to remove the adhesive, so that directional and large-area transfer can be achieved.

Referring to FIG. 6, the present invention provides a method for transferring graphene 200, which includes the following steps: S21, growing the graphene 200 on the growth substrate 100; S22, coating the adhesive layer 300 on the surface of the graphene 200 away from the growth substrate 100 to form a growth substrate/graphene/adhesive composite structure; S23, using the etching solution 600 to remove the growth substrate 100 is removed to form the graphene/adhesive composite layer; S24, the graphene/adhesive composite layer is disposed on a target substrate 700, and the graphene 200 is in direct contact with the target substrate 700; and S25, removing the adhesive layer 300.

The steps S21, S22, and S23 in the second embodiment are the same as the steps S11, S12, and S13 in the second embodiment, so they will not be repeated here.

In step S24, the graphene 200 is in direct contact with the target substrate 700, and the adhesive layer 300 is far away from the target substrate 700, that is, the graphene 200 is located between the target substrate 700 and the adhesive layer 300.

In step S25, an organic solvent is used to remove the adhesive layer 300, so the organic solvent is not limited, such as acetone and ethanol.

In this embodiment, the material of the adhesive layer is PMMA, and the etching solution 600 is _{a mixture of H 2} O ₂ , HCL, and DIW.

Furthermore, a comparative example is provided. In this comparative example, PMMA is used as the adhesive and ferric chloride solution is used as the corrosion copper growth substrate 100. That is, in the comparative example and this embodiment, except that the liquid for corroding the copper growth substrate is different (in the comparative example, the liquid for corroding the copper growth substrate is ferric chloride solution; in this embodiment, the liquid for corroding the copper growth substrate is The etching solution 600: _{a mixed solution of H 2} O ₂ , HCL and DIW), and the rest of the steps and materials are the same.

FIG. 7 is an optical photograph of graphene 200 after transfer using the method of the comparative example. In Figure 7, the black spots are residual iron oxide particles or copper oxide particles, and the bright spots are residual PMMA glue. FIG. 8 is a scanning electron micrograph of graphene 200 after transfer using the method of the comparative example. It can be clearly seen from Fig. 8 that there are granular objects and cracks, and the granular objects are residual iron oxide particles or copper oxide particles. It can be seen that when ferric chloride solution is used to corrode the copper growth substrate 100, a large amount of metal oxide particles and PMMA glue remain on the graphene 200, and the structure of the graphene 200 is destroyed.

FIG. 9 is an optical photograph of the graphene 200 after transfer using the method of this embodiment. In Figure 9, there are almost no bright spots, and black spots are greatly reduced. FIG. 10 is a scanning electron micrograph of the graphene 200 after transfer using the method of this embodiment. It can be seen from FIG. 10 that the graphene 200 is not damaged, the structure is complete, and there are no granular objects. It can be seen that _{when a mixture of H 2} O ₂ , HCL, and DIW is used as the etching solution 600, there are almost no metal oxide particles and PMMA glue residue on the graphene 200.

Further, FIG. 11 is a Raman spectrum of the graphene 200 after the transfer using the method of this embodiment. It can be seen from FIG. 11 that there is no D peak in the Raman spectrum at all, indicating that the etching solution 600 of this embodiment does not cause damage to the graphene 200 and does not introduce defects.

Furthermore, the adhesive layer 300 can be removed more completely by annealing. The annealing temperature can be selected according to the type of the adhesive layer 300.

The transfer method of the graphene 200 has the following advantages: First, a mixture of hydrogen peroxide, hydrochloric acid, and deionized water is used as the etching solution 600 to corrode the copper growth substrate 100, so that the graphene 200 is pure, free of iron oxide and oxidation. Particles such as copper exist; second, the method is simple and easy to implement.

In summary, this publication clearly meets the requirements of a patent for invention, so it filed a patent application in accordance with the law. However, the above descriptions are only preferred embodiments of the present invention, which cannot limit the scope of patent application in this case. All the equivalent modifications or changes made in accordance with the spirit of the present invention by those who are familiar with the art of this case shall be covered by the scope of the following patent applications.

100: growth base

200: Graphene

300: Adhesive layer

400: Graphene film

Claims (7)

A method for preparing a graphene adhesive film, comprising the following steps: growing a graphene on a growth substrate, the material of the growth substrate is copper; coating an adhesive layer on the surface of the graphene away from the growth substrate, Forming an adhesive/graphene/growth substrate composite structure; and using an etching solution to remove the growth substrate of the adhesive/graphene/growth substrate composite structure, the etching solution being hydrogen peroxide, hydrochloric acid and deionized water The volume ratio of the hydrogen peroxide, the hydrochloric acid and the deionized water is 1:1:50. The method for preparing a graphene adhesive film according to claim 1, wherein the method for removing the growth substrate using the etching solution includes the following steps: containing the etching solution in a container; and sticking the adhesive The composite structure of agent/graphene/growth substrate is placed in the etching solution, the adhesive layer is located above the graphene, and the growth substrate is located below the graphene; it is maintained for a period of time so that the growth substrate is corroded, Forming the graphene glue film, the graphene glue film floating on the surface of the etching solution; and removing the graphene glue film from the etching solution. The method for preparing a graphene adhesive film according to claim 2, wherein the method for removing the growth substrate using the etching solution further includes: placing the adhesive/graphene/growth substrate composite structure in the The step of removing a plurality of bubbles in the etching solution before the etching solution. The method for preparing a graphene film according to claim 3, wherein the method for removing the plurality of bubbles in the etching solution is to use a dropper to drive away the plurality of bubbles in the etching solution. The method for preparing a graphene adhesive film according to claim 4, wherein the method of putting the adhesive/graphene/growth substrate composite structure into the etching solution is to make the adhesive/graphene The/growth substrate composite structure is suspended in the etching solution. A method for transferring graphene, comprising the following steps: growing a graphene on a growth substrate, the material of the growth substrate is copper; coating an adhesive layer on the surface of the graphene away from the growth substrate, Forming a growth substrate/graphene/adhesive composite structure; providing an etching solution, the etching solution including a plurality of bubbles; Use a dropper to drive away multiple bubbles in the etching solution; use the etching solution to remove the growth substrate to form a graphene/adhesive composite layer, the etching solution is hydrogen peroxide, hydrochloric acid and deionized water The volume ratio of the hydrogen peroxide, the hydrochloric acid and the deionized water is 1:1:50; the graphene/adhesive composite layer is arranged on a target substrate, and the graphene and Direct contact with the target substrate; and removing the adhesive layer. The graphene transfer method according to claim 6, wherein the method for removing the growth substrate using the etching solution includes the following steps: holding the etching solution in a container; and using a dropper to transfer the etching solution Put the growth substrate/graphene/adhesive composite structure into the etching solution, the adhesive layer is located above the graphene, and the growth substrate is located on the top of the graphene Below; hold for a period of time so that the growth substrate is corroded to form the graphene/adhesive composite layer, the graphene/adhesive composite layer floating on the surface of the etching solution; and the graphene/adhesive The agent composite layer is taken out of the etching solution.

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